Gasification furnace for preparing superfine powder by using plasma transferred arc

Abstract

The utility model discloses a gasification furnace for preparing superfine powder by using plasma transferred arc. The gasification furnace comprises an outer thermal insulation layer, a conductive crucible, a crucible cover, a plasma gun layer and a plasma power supply. The crucible cover is arranged right above the conductive crucible to form an inner cavity, and the crucible cover and the conductive crucible are coated with the outer thermal insulation layer. One end of the plasma gun layer extends into the inner cavity, and the other end is connected with the cathode of the plasma power supply. A feeding channel and an air outlet channel are formed in the upper portion of the outer heat preservation layer and the crucible cover, and the opening position of the feeding channel is lower than that of the air outlet channel. The multi-layer electric conduction crucible is adopted, the effects of electric conduction, heat preservation and durability can be achieved, meanwhile, the upper end of the carrier gas channel is provided with the cavity surrounding the electric conduction crucible, carrier gas can be evenly preheated, and the gasification furnace is simple in structure, small in heat loss and stable and reliable in powder manufacturing process.

Description

Technical Field

[0001] This utility model relates to the technical field of ultrafine powder preparation equipment, specifically to a gasification furnace that uses a plasma transfer arc to prepare ultrafine powder. Background Technology

[0002] Existing gasification furnaces, such as the high-temperature reactor in Chinese patent CN118321565A, heat solid metal into metal vapor using a plasma transfer arc generated by a plasma spray gun inside the container. The metal particles generated in the metal vapor are then collected to obtain metal powder products. However, the crucible container for holding the material is generally made of high-temperature resistant, non-conductive ceramic material. A hole needs to be made at the bottom of the crucible to insert a conductive rod of the same material as the raw material, which is then connected to other conductors or wires from the bottom to form a conductive circuit. However, this operation has a significant impact on the service life of the crucible in high-temperature environments, and the crucible is difficult and costly to manufacture. It also makes the overall design and manufacturing of the gasification furnace more difficult. If the entire crucible is made of conductive metal or other materials, as in Chinese patent CN214260701U, the high-temperature material will damage the crucible, requiring frequent replacement and incurring high costs.

[0003] In addition, during the collection of metal powder, metal vapor needs to be extracted from the circulating airflow in the container. Due to the flow of the circulating airflow and the disturbance of the temperature and gas fields caused by the feeding, a stable metal heating and evaporation zone and a carrier gas flow zone are not formed in the container. This results in an uneven temperature field in the airflow of the carrier gas flow zone, with some areas having high temperatures and others having low temperatures. The metal particles formed by these metal vapors at different temperatures in the subsequent metal particle growth zone are of uneven size, leading to a high defect rate, low yield, and low production efficiency. Utility Model Content

[0004] To address the aforementioned problems in the prior art, this utility model provides a gasification furnace for preparing ultrafine powders using a plasma transfer arc, the specific solution of which is as follows:

[0005] A gasification furnace for preparing ultrafine powder using a plasma transfer arc includes: an outer insulation layer, a conductive crucible, a crucible lid, a plasma gun layer, and a plasma power source. The crucible lid is positioned directly above the conductive crucible, forming an inner cavity. The outer insulation layer covers the crucible lid and the conductive crucible. One end of the plasma gun layer penetrates the outer insulation layer and the crucible lid into the inner cavity, and the other end is connected to the negative electrode of the plasma power source. A feed channel and a gas outlet channel are formed in the upper part of the outer insulation layer and in the crucible lid. The opening of the feed channel on the crucible lid is lower than the opening of the gas outlet channel. The bottom of the outer insulation layer faces upwards. A gas channel is provided, with its upper end closely attached to the conductive crucible. The upper end of the gas channel is annular around the conductive crucible, and its middle and lower ends are tubular. The width of the annular channel is at least twice the inner diameter of the tubular channel. A carrier gas channel is connected to the top of the gas channel and extends into the conductive crucible along its upper edge. The conductive crucible comprises multiple layers, wherein the innermost layer and the outermost layer are conductive layers, and their tops are connected via the innermost layer. The bottom of the innermost layer has an opening, and the bottom of the innermost layer is exposed within the inner cavity. The bottom of the outermost layer is connected in the same arc to a graphite block connected to the positive electrode of the plasma power supply.

[0006] Furthermore, the conductive layer is made of graphite, zirconium boride, or a high-temperature resistant metal, and the innermost layer of the crucible is a ceramic crucible layer, preferably zirconium oxide with added calcium oxide stabilizer.

[0007] Furthermore, the outer insulation layer is a carbon felt-type insulation layer.

[0008] Furthermore, there is at least one crucible layer or sand filling layer between the innermost layer and the outermost layer of the crucible.

[0009] Furthermore, the number of carrier gas channels is 1-20.

[0010] Furthermore, the carrier gas channels are evenly distributed on both sides of the outlet gas channel.

[0011] Furthermore, the prepared ultrafine powders include tantalum powder, nickel powder, copper powder, silicon powder, and silver powder.

[0012] The beneficial effects of this utility model are:

[0013] The conductive crucible in this gasification furnace has a multi-layered structure. The innermost and outermost layers are conductive. The innermost crucible is made of zirconia with added calcium oxide stabilizer. Zirconia is a ceramic material with good wear resistance, high temperature resistance, and heat insulation properties. While protecting the innermost layer, it also prevents heat loss from the crucible. It has an opening at the bottom, allowing the bottom material to fully contact the conductive material of the innermost layer after the metal raw material is added. The innermost layer is made of zirconium diboride, a ceramic material with good wear resistance, high temperature resistance, and conductivity. The top layer directly contacts and covers all layers. The ring-shaped structure of the other layers (crucible layer and sand filling layer) allows the conductive inner and outermost layers to be interconnected. When metal material is added and current is applied, the current flows from the material through the innermost layer, the outermost layer, and the graphite block, connecting to the external conductor. This ensures that the current flows from the high-temperature material inside the crucible through the innermost and outermost layers to the outside, forming a complete electrical circuit with other wires, conductors, and the power source. Simultaneously, the wires are not directly connected to the crucible but rather to the graphite block, which is connected to the bottom of the crucible at the same arc, avoiding damage to the crucible during connection and ensuring repeated use. The entire crucible design solves the problems of poor conductivity in ceramic crucibles and the high cost and lack of durability of purely conductive crucibles.

[0014] Meanwhile, an outer insulation layer is wrapped around the outermost and bottom sides of the multi-layer heterogeneous conductive crucible, making full contact with the outermost layer to prevent heat loss from the inside of the conductive crucible, and also to support and fix the crucible. The opening of the feed channel in the inner cavity is set lower than that of the air outlet channel to prevent particulate powder in the material from being directly drawn into the air outlet channel during the falling process, which would result in a high defect rate of powder.

[0015] A gas channel is provided in the outer insulation layer. The upper end of the gas channel is in a ring shape that is close to the conductive crucible and then connected to the carrier gas channel. After the preheated gas is introduced into the gas channel, the temperature of the gas will be lost as it flows. Before entering the conductive crucible, it can be reheated around the conductive crucible. The portion of the carrier gas channel around the conductive crucible has a larger space than the middle and lower sections, allowing sufficient time for the carrier gas to be heated. This can further ensure that the airflow temperature field in the carrier gas flow area is more uniform, reduce the defect rate, and improve the yield and production efficiency. Attached Figure Description

[0016] The embodiments of this utility model will be further described below with reference to the accompanying drawings, wherein:

[0017] Figure 1 The diagram shows a front sectional view of the gasifier of this utility model.

[0018] Among them, 1—gasification furnace, 2—outer insulation layer, 3—gas channel, 4—conductive crucible, 401—secondary inner layer of crucible, 402—outermost layer of crucible, 403—graphite block, 5—carrier gas channel, 51—carrier gas inlet, 6—feed channel, 7—crucible cover, 8—plasma gun layer, 81—plasma arc, 9—gas outlet channel, 10—inner cavity, 11—material. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the scope of the present utility model.

[0020] In one embodiment, a gasification furnace 1 for preparing ultrafine powders (tantalum powder, nickel powder, copper powder, silicon powder, silver powder, etc.) using a plasma transfer arc includes: a carbon felt-like outer insulation layer 2, a conductive crucible 4, a crucible cover 7, a plasma gun layer 8, and a plasma power source. The crucible cover 7 is positioned directly above the conductive crucible 4, forming an inner cavity 10. The outer insulation layer 2 covers the crucible cover 7 and the conductive crucible 4. One end of the plasma gun layer 8 penetrates the outer insulation layer and the crucible cover 7 into the inner cavity 10, and the other end is connected to the negative electrode of the plasma power source. A feed channel 6 and an exhaust channel 9 are provided on the upper part of the outer insulation layer 2 and in the crucible cover 7. The opening position of the feed channel 6 on the inner side of the crucible cover 7 is lower than the opening position of the exhaust channel 9 on the inner side of the crucible cover 7. A gas channel 3 is provided at the bottom of the insulation layer 2, with the upper end of the gas channel 3 closely attached to the conductive crucible 4. The upper end of the gas channel 3 is annular around the conductive crucible 4, and the middle and lower ends are tubular. The width of the annular channel is at least twice the inner diameter of the tubular channel. The carrier gas channel 5 is connected to the top of the gas channel 3 and extends into the conductive crucible 4 along the upper edge of the conductive crucible 4. One end of the carrier gas channel 5 that extends into the inner cavity 10 is the carrier gas inlet 51. There are a total of 15 carrier gas channels 5, which are evenly distributed on both sides of the outlet channel 9. The conductive crucible 4 includes multiple layers. The innermost layer 401 of the crucible is made of zirconium boride, and the innermost layer of the crucible is made of zirconium oxide with added calcium oxide stabilizer. There are 1-3 crucible layers or sand filling layers between the innermost layer 401 and the outermost layer 402 of the crucible. The innermost layer 401 and the outermost layer 402 of the crucible are conductive layers, and their tops are connected via the innermost layer 401. The bottom of the innermost layer of the crucible has an opening, so that the bottom of the innermost layer 401 is exposed in the inner cavity 10. The bottom of the outermost layer 402 of the crucible is connected in the same arc to a graphite block 403 that is connected to the positive electrode of the plasma power supply.

[0021] Nitrogen, argon, hydrogen, or a mixture of two gases are introduced into the gasifier 1 through gas channel 3 until the system pressure reaches 100-300 kPa. The gas pressure inside the gasifier is maintained at this level for at least 20 minutes without leakage. After the airtightness test is passed, the vacuum pump is turned on until the system vacuum is less than 200 Pa. Nitrogen is then introduced to atmospheric pressure. This process of vacuuming and nitrogen purging is repeated at least three times until the oxygen content in the system is less than 500 ppm. The nitrogen environment within the system is maintained at 1-100 kPa. The distance between the cathode and anode is set to 0-50 cm. The plasma power supply is turned on, and the plasma current is set to 100-300 A. The arc ignition button is turned on, and a plasma arc 81 is formed between the cathode and anode. After the arc has been running stably for 1 hour, the current is gradually increased to increase the plasma operating power. The furnace is then preheated for at least 3 hours to bring the temperature of the main areas inside the furnace to the vaporization temperature of the metal material under this environment (e.g., 2500℃ for nickel). Once the temperature inside the crucible reaches the vaporization temperature, evaporation begins. Material 11 enters the conductive crucible 4 through the feed channel 6, maintaining stable operating current and voltage. The feeding rate of the feeding device is adjusted according to changes in the plasma operating voltage to maintain voltage stability.

[0022] The foregoing description describes some exemplary embodiments of this utility model. It is understood that the above embodiments are only used to explain this utility model and do not constitute a limitation on the scope of protection of this utility model. The features in these embodiments can be recombine in a suitable manner, and the resulting solutions are still within the scope of protection claimed by this utility model. Based on the above embodiments, all other embodiments obtained by those skilled in the art without inventive effort, that is, all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by this utility model.

Claims

1. A gasification furnace for preparing ultrafine powders using a plasma transfer arc, characterized in that, include: The outer insulation layer (2), conductive crucible (4), crucible lid (7), plasma gun layer (8), and plasma power supply are provided. The conductive crucible lid (7) is positioned directly above the conductive crucible (4) to form an inner cavity (10). The outer insulation layer (2) covers the crucible lid (7) and the conductive crucible. (4) In addition, one end of the plasma gun layer (8) passes through the outer insulation layer and the crucible cover (7) and enters the inner cavity (10), and the other end is connected to the negative electrode of the plasma power supply; the upper part of the outer insulation layer (2) and the crucible cover (7) are provided with a feed channel (6) and an exhaust channel (9), and the opening position of the feed channel (6) on the crucible cover (7) is lower than the opening position of the exhaust channel (9); the bottom of the outer insulation layer (2) is provided with a gas channel (3) facing upward, the upper end of the gas channel (3) is close to the conductive crucible (4), and the upper end of the gas channel (3) is an annular ring around the conductive crucible (4), and the middle and lower ends are tubular. The width inside the annular ring is at least twice the inner diameter of the tubular ring. The carrier gas channel (5) is connected to the top of the gas channel (3) and extends into the conductive crucible (4) along the upper edge of the conductive crucible (4); the conductive crucible (4) includes multiple layers, of which the innermost layer (401) of the crucible is... The outermost layer (402) of the crucible is a conductive layer and its top is connected via the innermost layer (401) of the crucible. The bottom of the innermost layer of the conductive crucible has an opening, and the bottom of the innermost layer (401) of the crucible is exposed in the inner cavity (10). The bottom of the outermost layer (402) of the conductive crucible is connected in the same arc to a graphite block (403) that is connected to the positive electrode of the plasma power supply.

2. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 1, characterized in that, The conductive layer is made of graphite, zirconium boride, or a high-temperature resistant metal, and the innermost layer of the conductive crucible is a ceramic crucible layer.

3. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 2, characterized in that, The innermost layer of the conductive crucible is made of zirconium oxide with added calcium oxide stabilizer.

4. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 1, characterized in that, There is at least one crucible layer or sand filling layer between the innermost layer (401) and the outermost layer (402) of the conductive crucible.

5. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 1, characterized in that, The outer insulation layer (2) is a carbon felt insulation layer.

6. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 1, characterized in that, The number of the carrier gas channels (5) is 1-20.

7. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 6, characterized in that, The carrier gas channels (5) are evenly distributed on both sides of the outlet gas channel (9).

8. A gasification furnace for preparing ultrafine powder using a plasma transfer arc according to claim 1, characterized in that, The prepared ultrafine powders include tantalum powder, nickel powder, copper powder, silicon powder, and silver powder.

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